Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $210.77   11.186%   $234.3467   $234.35   $234.35   $234.30  
  Purchase #2 $52.62   7.735%   $56.6902   $56.69   $56.70   $56.70  
  Purchase #3 $195.94   6.863%   $209.3874   $209.39   $209.40   $209.40  
  Purchase #4 $79.41   8.662%   $86.2885   $86.29   $86.30   $86.30  
  Purchase #5 $64.94   3.406%   $67.1519   $67.15   $67.15   $67.20  
  Purchase #6 $195.81   11.678%   $218.6767   $218.68   $218.70   $218.70  
  Purchase #7 $77.95   3.205%   $80.4483   $80.45   $80.45   $80.40  
  7 purchase totals = $877.44       $952.9897   $953.00   $953.05   $953.00